Even though it’s been less than a year since the launch of Google+, there are already 90 million people who have joined this emerging social network.

Some analysts predict that by the end of 2012, the Google+ community will surpass 400 million people. That may be far behind Facebook’s 800 million members, but it still represents an impressive growth rate.

To make things easier for people who are still getting up to speed on the world of Google+, here are 20 terms and definitions you need to know in order to join the conversation and community on Google+.

Basic Google+ Terms

The Google+ terms in this section are ones that you might already be familiar with from other social networking sites. They’re fairly easy to understand and should make sense to you regardless of your technical abilities or specific knowledge of the Google+ platform.

1. Badges: Google+ Badges are widgets that you can place in your blog or website sidebar. Similar to Facebook’s “Like Box” widgets, Google+ Badges make it easy for you to promote your Google+ Profile or Page and for people to add you to their Google+ Circles right from your website.

2. Chat: Using the Chat feature, you can notify people in your Google+ Circles that you’re online and available for an online chat from within Google+.

3. Hashtag: If you use Twitter, then you’re familiar with hashtags, which are used to keep track of content related to a specific topic and are identified by a keyword preceded by the “#” symbol (e.g., #socialmedia).

4. Notifications: You can configure your Google+ Account so you receive notifications by email, text message, or in the Google Bar when something happens that involves you, such as when you’re tagged in a photo, a post is shared with you, or someone adds you to a Circle.

5. Profile: A Google+ Profile is an individual’s place on Google+ where he or she publishes and shares content, and interacts with the Google+ community.

6. Page: Google+ Pages are created and used by businesses and brands, while individuals create Google+ Profiles.

7. Stream: Your Google+ Stream is where the updates from Google+ members in your Circles appear. It is updated in real-time. The text box at the top of the Google+ Stream is where you can enter your own updates and share photos and videos with people who have you in their Circles.

8. Sharing: As a Google+ member, you can share content (text, images, video, and links) by publishing it as an update to your Google+ Stream. When you share content, it’s visible on your own Google+ Stream and on the Streams of people that you chose to share that content with who have you in their own Google+ Circles. You can also “re-share” content that other Google+ members shared in their own Streams.

9. Tag: You can tag other people in your Google+ updates and other people can tag you in their updates. To tag someone in an update, type “+” or “@” before the person’s name (minus the quotes), and that person will receive a notification (if their notifications are turned on).

Advanced Google+ Terms

While the features and the Google+ terms discussed below might not technically be advanced, the terminology is. If you’re new to Google+, these terms may be the ones that will have you asking, “What is that?”

10. +1 Button: Similar to the Facebook Like button and the Twitter Tweet button, the +1 button is included on websites to make it easy for people to share content with their Google+ Circles. When you see the +1 button, click it to share a link to the content as an update in your Google+ Stream.

11. Circles: You can organize the people you follow on Google+ and the people who follow you, by grouping them into Circles. For example, you can create a family Circle, a work Circle, and a friends Circle. You can create Circles in any way you choose to best organize your followers. When you publish content on Google+, you can choose which Circles to share that content with; you can share the content with everyone in all of your Circles or make it public for anyone to see.

12. Data Liberation: Use this feature to download and backup the content in your Google+ Account, which is available through the Google+ Settings option (the gear icon in the upper-right corner of your screen when you’re logged into your Google+ account).

13. Extended Circles: This is a confusing concept, but it’s important! When you share content with your extended Circles, people might be able to view your content even if you don’t know them. You can’t see a list of people in your extended Circles, because Google claims the list is constantly changing. Here is how extended Circles work according to Google:

Imagine that Mary is in one of your Google+ Circles, and John is in one of Mary’s Circles. You don’t know John, and he’s not in any of your Circles. If Mary chooses to have John visible on her Profile (as one of the people in her Circles), and you choose to share an update with your extended Circles, then your content could appear in John’s Stream and be visible to John on the Posts tab of your Google+ profile.

In other words, when you post content on Google+, be prepared that your content may be visible to people outside your immediate network of Circles.

14. Google Bar: The Google Bar (also called the Google+ Bar or Sand Bar) is the gray bar that appears across the top of your screen when you’re logged into your Google Account and visiting any Google product web page. You can see your Google+ notifications and share content on Google+ with a single click from the Google Bar.

15. Hangouts: Using the hangouts feature, you can video chat with up to 10 other people.

16. Hangouts on Air: Hangouts on Airs are produced by Google+ and are publicly aired live to the world on Google+ and YouTube. Hangouts on Air are also made available for playback at a later time. 10 people can join the hangout. Once the hangout is full, you can’t join and participate via video, but you can watch it as a YouTube video from the Stream.

17. Instant Upload: Using Instant Upload, you can share photos that you take with your mobile phone to your Google+ Circles. Just give Google+ permission to add your pictures to a private photo album that’s hosted in the cloud, and your photos will be available for you to access from any device and share on Google+ whenever you’d like.

18. Messenger: This feature was originally called Huddle. Though the name changed, the functionality still enables you to turn conversations between a group of people into a group chat with your mobile device.

19. Ripples: Google+ Ripples is the name of a tool that helps you visualize how content is shared and discussed across the Google+ community. You can click any public post on Google+ and select the “View Ripples” option to view the activity related to that update, including top contributors and much more.

20. Saved Search: Formerly called Sparks, saved searches make it easy for you to follow Google+ updates related to a specific keyword or keyword phrase that interests you.

Have we missed anything? Let us know your thoughts about these terms or Google+ in general, in the comments below.

[Sources: Google, Paul Allen; Images: Audio Visual Junkie, timubl, Charlie Wollborg]